1. Field of the Invention
This invention relates generally to laser and focused ion beam tools for repairing semiconductor-wafers, and particularly, an enhanced software technique for modifying operator indicated repair areas based on laser and focused ion beam effects.
2. Discussion of the Prior Art
In laser and focused ion beam repair tools, an operator views an image (in real time on a computer) of a semiconductor wafer/mask that may have some defects on it, e.g., material that must be removed from the wafer/mask to make it functional. When the operator locates a defect, he uses the computer-based control system to draw an outline around the defect that needs to be removed. The computer software then translates the screen coordinates into real world coordinates and either moves the laser/ion beam or the stage on which the wafer/mask sits, in order to have the laser/ion beam impinge on the defect within the area outlined by the operator.
When a tool operator draws enclosed shapes that indicate an area to be ablated of material by either a laser or ion beam, the size of the beam must be taken into account when the beam actually scans the area. FIG. 1(a) depicts a polygonal line segment 15 representing an outline of an area 20 that an operator wishes to repair. The circles 22 represent the diameters of the beam which are of the order of less than {fraction (1)} a micron in diameter. As known, the laser beam, modulated by an optical shutter such as a Pockels cell, is scanned across the actual wafer/mask 10, for example, in a horizontal direction to do the repair. Particularly, the optical shutter is closed during scanning outside of the outlined segment 15, and is opened when scanning beam is within the desired area 20. As shown in FIG. 1(a) some of the outlined segment edges, e.g., edge 16, intersects with the laser beam circles, e.g., circle 22a, and the operator must make a decision as to whether to open or keep the shutter closed. To illustrate the bias effect, FIG. 1(b) is a graphical representation of a repair outline 15 of area 20 as in FIG. 1(a) when implementing a laser beam tool generating beams of increased beam size, i.e., a Pockels cell shutter forming laser/ion beam having a circle diameter 23. FIG. 1(b) thus illustrates the basis for applying bias effects to a repair according to the prior art, which is to change the beam circle radius. Application of this bias technique requires numerous calculations against intersections with the line segments, and are subject to rounding errors, spot misplacements, and failure when a piece of the shape to be repaired is removed after applying bias.
Other techniques for applying bias relied on moving the line segments that form the polygon computationally. This leads to a non-deterministic situation since some operator drawn shapes would cause these methods to fail. That is, the situation is non-deterministic because there are no restraints on what kind of shapes the operator might draw, nor on what the bias at any particular application might be. The typical failure mode occurs when vertices and line segments need to be removed as a result of applying bias corrections.
It would be highly desirable to provide a laser/ion beam bias technique that is operator-friendly, simple to implement, and results in accurate repairs of wafer/mask defects.
It is an object of the present invention to provide a graphical technique for modifying an enclosed area for ion beam and laser beam bias effects that is speedier and more accurate than prior art techniques which are largely computational.
It is another object of the present invention to provide a graphical technique for modifying an enclosed area for ion beam and laser beam bias effects using standard graphical tools available in most programming languages.
According to the invention, there is provided a system and method for repairing defects in semiconductor wafers utilizing a repair tool including a device for applying energy to obliterate defects at locations on the wafer, the method being a graphical approach implementing a graphical user interface (GUI) comprising a pixel screen display and comprising the steps of: via the interface, identifying a wafer defect to repair and enclosing the defect within a polygonal repair outline drawn using a default line thickness; graphically adjusting the line thickness to modify the enclosed polygonal repair outline area; automatically detecting one or more areas within an interior region of the modified polygonal repair outline area; and, scanning the modified polygonal repair outline, and for each pixel location inside the one or more detected areas, applying energy to the wafer coordinated to the pixel location for repairing the defect, whereby the identification of said pixel location is accomplished using standard graphical tools with minimal operator intervention.
Advantageously, such a system and method of the invention is applicable in a manufacturing environment. Standard graphical tools are used as opposed to large amounts of custom software. Accordingly, computational complexity of repair operations and errors due to round offs with floating point numbers are eliminated. Moreover, due to the largely automatic process, operator error is minimized. As a result, the speed and accuracy with which repairs defects are performed is significantly enhanced.